@Override
    public NavigableMap<K, V2> subMap(
        @ParametricNullness K fromKey,
        boolean fromInclusive,
        @ParametricNullness K toKey,
        boolean toInclusive) {
      return transformEntries(
          fromMap().subMap(fromKey, fromInclusive, toKey, toInclusive), transformer);
    }

    @Override

    @Override
    public NavigableMap<K, V2> subMap(
        @ParametricNullness K fromKey,
        boolean fromInclusive,
        @ParametricNullness K toKey,
        boolean toInclusive) {
      return transformEntries(
          fromMap().subMap(fromKey, fromInclusive, toKey, toInclusive), transformer);
    }

    @Override

        assertEqualInOrder(
            entries.subList(i, j),
            navigableMap.subMap(entries.get(i).getKey(), entries.get(j).getKey()).entrySet());
      }
    }
  }

  @CollectionSize.Require(SEVERAL)
  public void testSubMapIllegal() {
    assertThrows(IllegalArgumentException.class, () -> navigableMap.subMap(c.getKey(), a.getKey()));
  }

  @CollectionSize.Require(absent = ZERO)

   * This method returns a {@code ImmutableSortedMap}, consisting of the entries whose keys ranges
   * from {@code fromKey}, inclusive, to {@code toKey}, exclusive.
   *
   * <p>The {@link SortedMap#subMap} documentation states that a submap of a submap throws an {@link
   * IllegalArgumentException} if passed a {@code fromKey} less than an earlier {@code fromKey}.
   * However, this method doesn't throw an exception in that situation, but instead keeps the

    return Maps.keyOrNull(higherEntry(key));
  }

  abstract Iterator<Entry<K, V>> descendingEntryIterator();

  @Override
  public SortedMap<K, V> subMap(@ParametricNullness K fromKey, @ParametricNullness K toKey) {
    return subMap(fromKey, true, toKey, false);
  }

  @Override
  public SortedMap<K, V> headMap(@ParametricNullness K toKey) {
    return headMap(toKey, false);
  }

  @Override

          .rowMap();
    }

    @Override
    public SortedMap<R, Map<C, V>> subMap(R fromKey, R toKey) {
      checkNotNull(fromKey);
      checkNotNull(toKey);
      return new StandardRowSortedTable<R, C, V>(sortedBackingMap().subMap(fromKey, toKey), factory)
          .rowMap();
    }

    @Override
    public SortedMap<R, Map<C, V>> tailMap(R fromKey) {

    }

    @Override
    public Entry<K, V>[] createArray(int length) {
      return delegate.createArray(length);
    }
  }

  /** Two bounds (from and to) define how to build a subMap. */
  public enum Bound {
    INCLUSIVE,
    EXCLUSIVE,
    NO_BOUND;
  }

  public static class SortedSetSubsetTestSetGenerator<E extends @Nullable Object>
      implements TestSortedSetGenerator<E> {

          .rowMap();
    }

    @Override
    public SortedMap<R, Map<C, V>> subMap(R fromKey, R toKey) {
      checkNotNull(fromKey);
      checkNotNull(toKey);
      return new StandardRowSortedTable<R, C, V>(sortedBackingMap().subMap(fromKey, toKey), factory)
          .rowMap();
    }

    @Override
    public SortedMap<R, Map<C, V>> tailMap(R fromKey) {

    extends AbstractImmutableSortedMapMapInterfaceTest<String, Integer> {
  @Override
  protected SortedMap<String, Integer> makePopulatedMap() {
    return ImmutableSortedMap.of("a", 1, "b", 2, "c", 3, "d", 4, "e", 5).subMap("b", "d");
  }

  @Override
  protected String getKeyNotInPopulatedMap() {
    return "a";
  }

  @Override
  protected Integer getValueNotInPopulatedMap() {
    return 4;
  }

    extends AbstractImmutableSortedMapMapInterfaceTest<String, Integer> {
  @Override
  protected SortedMap<String, Integer> makePopulatedMap() {
    return ImmutableSortedMap.of("a", 1, "b", 2, "c", 3, "d", 4, "e", 5).subMap("b", "d");
  }

  @Override
  protected String getKeyNotInPopulatedMap() {
    return "a";
  }

  @Override
  protected Integer getValueNotInPopulatedMap() {
    return 4;
  }